Radioactive Takumar M42 lenses

We all know about certain Takumar lenses and their radioactivity (not Alpha radiation though - thank god!)
Alright on film bodies, but what happens on Digital bodies?
Obviously the sensor is electronic, but would the radiation from these lenses damage or at the very least affect the image the sensor takes?

I am intrigued.

I once visited a company that sterilised medical materials using short bursts of hi-energy radiation.

Part of the safety proceedures required before the lethal rays could be unleashed was that they had to check there was no one in the chamber. This was done with 'hardened' video cameras, actually in the chamber.

The life of these cameras was measured in months as the image simply got darker and darker until not aceptable. I don't know if the sensor was affected, but the glass of the lenses were clearly darkened by exposure.


On another tack - I recall reading that micro electronic circuits (of which a sensor is one) are susceptable to damage by cosmic rays (they knock of the electrons from any atom they hit) as they (the circuits) get smaller and smaller.


Doesn't answer your query, but I would guess that if you are safe to handle the lenses then the camera as a whole is safe.

regards
Bernard

Typical low energy alpha particles would be of little concern in this sort of application as they are stopped by the thin layer of dead skin on the outside of your body, or a few cm of air, the glass of the viewfinder would be quite enough to stop any getting to your eye. They only become a significant hazard internally, as there they readily contact living cells. Active dust is probably the most serious hazard with alpha radiation as this opens up the possibly of ingestion/inhalation.

I don't have actual data on the activity of the glass used in those Takumar lenses, but I suspect the levels are exceeded my many everyday situations. Living in Cornwall, flying, eating brazil nuts... all significantly increase your background exposure to radioactivity.

Beta & gamma radiation travel further (a few mm of lead stops beta) but are less ionising.

I'd expect both types of sensor used in cameras (CMOS & CCD) to record radioactive particles in the same way that film will. Occasionally such interactions will damage the sensor giving either a hot pixel or a dead one. Quite a lot of random pixels can be effected like this before you're likely to notice unless you go looking for them.

I've never heard of this radioactive lens issue...thought the only thing i needed to worry about was whether my Pacific tuna or salmon was affected!

The only thing you need worry about is the glass takes on a yellow tinge. That can be corrected by leaving the lens in UV light, normally in sunlight for a few days. It is only a problem with a small number of high end Takumar lenses such as some of the 50mm f/1.4 lenses.

K.

A quick investigation suggests the activity within 1cm of the most active is ~2µSv/hr - about 1/5th the extra activity you'd be exposed to when flying at 30,000ft. Professional airline pilots flying at this altitude roughly 65hrs a month supposedly have a roughly 1% increased risk of cancer, so if you're very much in love with your Takumar lens you MIGHT be get a measurable increased risk - I wouldn't want to sleep with my lenses though, they might get fungus

It also seems that the initial radiation IS alpha (for both isotopes of Thorium used in the glass), this is all stopped by other lens elements. After undergoing radioactive decay the subsequent decay steps can involve beta radiation.

This Link on Thoriated camera lenses might be interest.

Fish from the Irish sea are more likely to be an issue for you - but as Kris says there's no need to worry. The levels are very low & observations of the recovery around Chernobyl have lead to some controversial suggestions that constant moderately high background radioactivity may even be beneficial...

http://web.aanet.com.au/bayling/repair.html

http://www.luminous-landscape.com/columns/sm-02-11-24.shtml